Armature adjusting structure



17, 1965 w. w. POULTON, JR., ETAL 3,201,659

ARMATURE ADJUSTING STRUCTURE Filed NOV. 20, 1962 2 Sheets-Sheet 1 A M \2 I 207 L D Md INVENTORS WILSON w. PUULTON, .m. n-'2 MARY K. POULTON, [EXECUTE/X) ALBERT STROBEL.

1965 w. w. POULTON, JR, ETAL 3,201,659

ARMATURE ADJUSTING STRUCTURE Filed Nov. 20, 1962 2 Sheets-Sheet 2 INVENTORS WILSON W. POULTON, JR (DECEA:E|J MARY K. POULTON, ('Exzzcu'rR/x) ALBERT STROBEL.

United States Patent 3,201,659 ARMATURE ADJUSTING STRUCTURE Wilson W. Poulton, Jr., deceased, late of Broomall, Pa.,

by Mary K. Poulton, executrix, Broomall, Pa., and

Albert Strobel, Cherry Hill, N.J., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Nov. 20, 1962, Ser. No. 239,096 5 Claims. (Cl. 317176) This invention relates to circuit breakers and more particularly to a novel armature adjustment structure for magnetic instantaneous trip means enabling the magnetic air gap to be easily, rapidly and reliably adjusted.

Automatic circuit breakers are usually provided with instantaneous trip means comprising a magnetic structure which, when subjected to overload currents of any predetermined magnitudes, actuates a mechanism which in turn causes a tripper bar to be urged into rotational movement. The tripper bar in turn releases a latch mechanism which is held in a position to restrain an energized opening spring from moving to its de-energized state. In this condition the circuit breaker contacts are kept in the closed, or engaged position. Upon release of the latch mechanism the operating spring is thereby enabled to move to its de-energized state thereby rapidly separating the circuit breaker cooperating contacts. This operation occurs at speeds suflicient to interrupt the current so as to prevent any harm to befall the elements of the circuit being protected by the circuit breaker.

The adjustment of the magnetic trip means is chosen so as to initiate an instantaneous tripping action during the occurence of a fault condition having a high current magnitude. Since the magnetic trip means does operate during extremely high current faults, it is necessary that the operation be both rapid and reliable. It is therefore necessary to adjust the magnetic trip means to operate immediately upon the occurrence of high current faults of a predetermined magnitude.

Since the circuit breaker may undergo a number of closing and tripping operations during its useful operating life, the mechanical parts undergo a significant amount of wear. The wearing of these parts may so effect the critical adjustment of the elements of the circuit breaker as to severely effect the timing of the instantaneous trip means so that the trip means fails to operate at the predetermined fault current magnitudes for which it was originally adjusted. in addition to such operation, the adjustment of the instantaneous trip means may be necessary, due to the use of the circuit breaker in a variety of dirierent applications wherein each individual application has a different fault current condition to which the instantaneous magnetic trip means must be responsive. It is thereby quite advantageous to provide an armature adjustment structure enabling safe, rapid and reliable adjustment of the magnetic trip means without the necessity for complex tools or a tedious adjusting operation, whether the adjustment be required for purposes of compensation for wearing of parts, or for adjusting a circuit breaker to react according to a predetermined fault current condition.

The assembly of the instant invention acts to provide all of the above features, while at the same time being constructed so as to be easily operated without the necessity for any complex tools or manual manipulations and is further constructed so as to be comprised of a minimum of parts which elements are arranged so that movement of the adjusting structure operating button directly imparts movement to the instantaneous trip means armature member without the necessity of providing additional linkages or connections therebetween.

The assembly of the instant invention is comprised of an adjusting button mounted for rotational movement within the confines of a bracket member and having a retaining pin and a biasing means for positioning and securing the adjusting member relative to the supporting bracket. A first end of the adjusting member is adapted to receive an adjusting tool for imparting rotation thereto. The opposite end of the adjusting button has a cammed surface which is so constructed as to cooperate with a projecting ear mounted to the magnetic trip means armature which when moving the ear, directly imparts movement to the armature member. The lower end of the adjusting button is further provided with a plurality of grooves in close proximity to the cam member, which cooperate with the biasing spring in order to lock the adjusting button in a plurality of discreet positions, which positions may be selected in any arbitrary manner in order to properly position the armature member of the magnetic trip assembly.

The holding bracket and ear members are so designed as to be easily installable in circuit breakers which are presently in use, as well as in new circuit breaker structures, thereby readily adapting themselves for employment in a wide variety of circuit breaker applications and structures. The biasing means, in addition to maintaining the vertical alignment of the adjusting member is further constructed to cooperate with the plurality of grooves provided in the adjusting member in order to properly position the magnetic means armature member in a variety of arbitrary angular orientations. The plurality of functions which each element of the adjusting structure provides thereby substantially optimizes the number of elements which comprise the armature structure to a minimum, while at the same time providing a safe, accurate and reliable adjusting structure. The arrangement is further so constructed as to provide direct movement of the armature member in response to movement of the adjusting button member without the necessity of any linkages therebetween. Also, the adjusting button member need only be rotated, either clockwise or counterclockwise for positioning the armature member and need not undergo any other movement in order to provide for the adjusting operation.

It is therefore one object of this invention to provide an armature adjustment assembly for circuit breaker magnetic trip means having a novel construction for directly imparting movement of the structure adjustment button directly to the magnetic means armature member.

Another object of this invention is to provide a novel armature adjustment structure for circuit breaker magnetic trip means which is so constructed as to undergo only rotational movement for adjusting the magnetic trip means armature member.

Still another object of this invention is to provide an armature adjustment assembly for a circuit magnetic trip means having a cam surface for smoothly and uniformly operating the magnetic means armature member.

Another object of this invention is to provide an annature adjustment for circuit breaker magnetic trip means which is provided with biasing means, for performing the dual function of positioning and securing the adjustment button and for aligning the armature member in a plurality of predetermined discreet positions.

Still another object of this invention is to provide an armature adjustment assembly for circuit breaker magnetic trip means which is constructed as to be readily adaptable to any present day magnetic trip structures.

These and other objects will become apparent when reading the accompanying description and drawings in which:

FIGURE 1 is a perspective view showing the novel armature adjustment assembly of the instant invention 33 and some of the cooperating elements of a typical circuit breaker in which the adjustment assembly may be employed.

FIGURE 2 is an elevational view in the direction of arrows 22 shown in FIGURE 1.

FIGURE 3 is an elevational view of the structure of FIGURE 1 looking in the directions of the arrows 3-3 shown in FIGURE 1.

FIGURE 4 is a top view of a portion of the adjustment assembly of FIGURE 2 taken in the direction of arrows 4--4.

FIGURE 5 is a top view of the adjustment button shown in FIGURES 1-3 looking in the direction of arrows 5-5.

Referring now to the drawings and more particularly to FIGURES 13, the magnetic adjustment assembly which is generally designated by numeral 200 is mounted within a circuit breaker assembly 100 having a wall 101 for receiving the armature adjustment assembly mounting bracket 201. Only a very limited portion of the circuit breaker 100 has been portrayed in FIGURE 1 for the purposes of clarity, but it should be assumed that the circuit breaker 100 is comprised of a pair of cooperating contacts which may be operated to their open position by both a manual means and at least a magnetic trip means and the manual means may be operable for any purpose, while the magnetic trip means is designed to provide a tripping operation upon the occurrence of high magnitude current faults in the circuit being protected by the circuit breaker. A circuit breaker of this general type is set forth in US. application No. 132,046 entitled Assembly of Circuit Breaker Mechanism, filed August 17, 1961, by Wilson W. Poulton, Jr. and assigned to the assignee of the instant invention A detailed description of such a circuit breaker is unnecessary for purposes of the instant invention and the aforementioned US. application is thereby incorporated herein by reference thereto.

For purposes of understanding the device of the instant invention it is sufiicient to say that the circuit breaker 100 is provided with a tripper bar 102 mounted in close proximity to the wall 101 of circuit breaker 100 wherein said tripper bar 102 is mounted to rotate in both the clockwise and counterclockwise directions, as shown by arrows 104 and 103, such that the tripper bar 102 rotates about its central axis represented by phantom line 105. The tripper bar 102 is biased, by means not shown, in the clockwise direction, shown by arrow 104, so that the surface 106 of its lower end 102a is in close proximity with the projection of the magnetic armature means 303, for a purpose to be more fully described. counterclockwise rotation of tripper bar 102 causes release of the circuit breaker latching mechanism (not shown), which releases the circuit breaker operating spring (not shown) for movement of the circuit breaker cooperating contacts (not shown) to their fully disengaged position thus cutting off current flow of the circuit being protected.

The tripper bar 102 shown in FIGURE 1 may be of a length greater than that shown by magnetic means 200 in FIGURE 1 in order to protect multi-phase electrical distribution systems, such as for example, the widely used three-phase electrical systems, which systems are provided with three magnetic structures of the type shown by structure 200 in FIGURE 1 wherein each magnetic assembly protects its individual associated phase of the three-phase system. I

The magnetic structure 300 is comprised of a magnetic core member 301 supported in a substantially U shaped metallic frame 305. The magnetic core member 301 is a substantiallyU-shaped core member having an energizing winding 302 surrounding the yoke (not shown) of the U-shaped member 301, in order to generate a strong magnetic flux pattern in the magnetic core member 301 Although it is not shown in any of the figures, it should be understood that the winding 302 is connected in series with the circuit being protected in order to generate a flux pattern of sufficient magnitude so as to attract the magnetic structure armature member 303 for imparting rotation to the tripper bar 102, in a manner to be more fully described.

The energizing winding 302 is formed of a plurality of substantially thin fiat copper sheet members 302a which surround the core member 301. The sheet members then extend through an opening 303a in the armature member 303 and are joined with a terminal bar 304, having suitable apertures 304a for mounting in the co operating contact current path and in series therewith.

The magnetic means armature member 303 is a sub stantially flat member, the lower projections 3031b and 303s being positioned in suitable openings 305a in the U-shaped holding structure 305, enabling the armature to be pivoted about its lower ends in the directions shown by arrows 306 and 307. It should be understood that movement in the direction 306 is in response to an instantaneous magnetic tripping operation, in a manner to be more fully described.

The armature member 303 is biased in the direction shown by arrow 307 by spring means 303 and 308a. The upper end of spring means 308 engages turned out tabs 303d at the upper right-hand corner of armature member 303, while the lower end of spring member 308 engages an elongated pin 309 which is mounted in suitable openings provided at the extreme front edges of the U- shaped holding, or supporting structure 305. Spring means 308a has its lower end engaged by pin 30? and its upper end engaged by L-shaped member 320. A projection 311 is provided at the upper end of armature member 303 and substantially intermediate its left and right hand edges for the purpose of engaging the surface 106 of the lower portion 102a of tripper bar 102. A tapped aperture 312 is provided in projection 311 for receiving a screw member 313 employed for the purpose of adjusting the armature member 303 relative to the tripper bar 102.

The operation of the magnetic assembly is as follows:

When fault current of a predetermined magnitude flows through the circuit being protected, the energizing winding 302, being in series connection with the circuit being protected, generates a magnetic flux pattern in the core member 301. When this magnetic pattern reaches a predetermined magnitude the faces of the magnetic core member 301 act to attract the armature member 303 causing the armature member to rotate in a direction shown by arrow 306 towards the pole faces of the core member 301. It should be understood that the magnetic field will be of a sufficient strength to overcome the biasing force imposed upon armature member 303 by the spring means 308 and 30811. The projection 311, likewise moves in the direction shown by arrow 306, thereby coming into engagement with the surface 106 of tripper bar 102. As the armature member 303 moves still further in a direction shown by arrow 306, this movement, through projection 311 and adjusting screw member 313, is imparted to the tripper bar 102 causing it to rotate in the direction shown by arrow 103, about its longitudinal axis 105. After a predetermined amount of rotation is experienced by tripper bar 102, a latch (not shown) is caused to move to its unlatched position under control of the tripper bars rotation, thereby enabling the circuit breaker cooperating contacts (not shown) to move to their fully disengaged position.

It can readily be seen that the positioning of the armature member 303 relative to the pole faces of the core member 301 is directly determinative of the magnetic'field pattern which must be generated by the energizing winding 302 for the purpose of providing an instantaneous tripping action. Since the circuit breaker may be so designed as to be useful in a variety of different circuit applicationsit becomes advantageous to provide cations for which the circuit breaker 100 may be employed, all of which applications may require different magnetic trip means adjustments.

In order to provide these necessary adjustments the adjustment structure 200 is provided, which structure 200 is comprised of a supporting bracket 201, having a suitable aperture 202 for receiving fastening means 203 enabling the support member 201 to be secured to the wall 101 of circuit breaker 100. The support member 201 has a substantially U-shaped portion 205, having an upper arm portion 206 with a suitable aperture 204 for receiving the adjusting rod 207 therethrough. The lower arm 208 also has a suitable aperture (not shown) for receiving the adjusting rod 207. The adjusting rod 207 is provided with a suitable aperture 207a for receiving a pin 210. The dimensions of the pin 210 are such that its length is substantially greater than the diameter of the rod 207 and substantially greater than the diameter of the aperture 204 thereby preventing any movement of the adjusting rod 207 in the downward, vertical direction, as shown by arrow 212, when the pin member 210 engages the upper surface of the supporting bracket 201.

The lower arm 208 of the substantially U-shaped portion 205 has a spring member 214 of substantially U- shaped configuration (see FIGURE 4) secured to the arm 208 at its front end 214a by suitable fastening means 215. The arm 217 of U-shaped spring member 214 is provided with an ear portion 217a which ear portion has a substantially U-shaped profile, as can best be seen in FIGURES 2 and 1. Arm 216 has no U- shaped ear portion and is provided to equalize the biasing force imposed upon adjusting rod 207.

The adjusting rod 207 is provided with a flanged portion 220 having a diameter substantially greater than that of its body portion 207 and is so arranged that the upper surface 221 makes contact with the ear portion 217a and arm 216 of spring member 214. Spring member 214 is biased in such a manner as to urge adjusting rod 207 in the downward, vertical direction, as shown by arrow 212. Thus, it can be seen that the holding pin 210 and the biasing spring 214 act to hold the adjusting rod 207 substantially motionless, relative to the vertical direction, while enabling the rod 207 to rotate in the opposing directions 230 and 231 for the purpose of adjusting the air gap between armature and core 303 and 301, respectively, in a manner to be more fully described. The upper surface 221 of flange 220 is provided with a plurality of radially aligned grooves 222 for receiving the ear portion 217a so as to enable positioning of the adjusting rod 207 in a plurality of predetermined, discrete, angular positions, for purposes to be more fully described.

The lower surface 223 of the flanged portion 220 is provided with a projection 224, having a cammed surface 225 which is employed for moving the magnetic means armature member The surface of the projection 224 is eccentric, as can most clearly be seen in FIGURE 1, so that the rotational motion of adjusting rod 207 may be converted into substantially linear motion of the upper end of magnetic means armature member 303, as will become more evident.

The armature member 3ti3 is further provided with a substantially L-shaped bracket 235 suitably secured to armature member 303 at its lower end by fastening means 236. Adjusting screw 237 is provided in a tapped aperture 233 in member 235 for a purpose to be more fully described. The member 235 has a forwardly extending contact surface 336 which is positioned so as to make sliding engagement with the eccentric s rface 225 or" projection 224 provided on adjusting rod 207.

The arrangement is such that upon rotation of the adjusting rod 207, the eccentric surface 225 bears against the contact surface 336 of L-shaped member 235. The member 235 is urged in a direction shown by arrow 307 due to spring means 303 and further due to the fact that L-shaped member 235 is rigidly secured to armature member 363. As the adjusting rod 207 is rotated, either clockwise or counterclockwise, through a full cycle of rotation, the eccentric surface 225 of the lower projection 224 causes the L-shaped member 235 to move substantially linearly in a substantially reciprocating manner, thereby running the armature member 303 through its full cycle of adjustable air gap positions. It should be understood that the adjusting rod 207 may be locked in any one of a plurality of discrete positions so as to select a predetermined air gap dimension. This is provided for in the following manner:

As the adjusting rod 207 is rotated in either of the two directions shown by arrows 230 and 231, the flanged portion 220 of rod 207 has the same rotation imparted to it, thereby causing the ear 217a to be moved out of the grooves 222 provided on the top surface of flange 220. For example, in the position shown in FIGURE 1 of the drawings, if the adjusting rod 207 is rotated in the direction shown by arrow 231 the ear 217a is urged out of engagement with the groove 222a. As the rod 207 is rotated still further in the direction shown by arrow 231, the groove 22252 will move to a position immediately beneath ear 217a thereby causing biasing member 214 to urge the ear 217a downward into the groove 22211. This locking motion can easily be felt by the operator making the magnetic air gap adjustment and in addition thereto furthe requires that the party making the adjustment impart slightly more rotational force to the adjusting rod 207 in order to lift ear 217a out of groove 22211.

It should be understood that the radially aligned grooves 222 may be positioned in any angular orientation desired, dependin strictly upon the magnetic air gap dimensions desired by the individual circuit breaker applications.

The adjusting screw 313 is provided on armature projection 311 in order to regulate the desired moment at which the tripper bar unlatching operation should be initiated relative to the movement of the magnetic means armature member 303. The adjusting screw 237 provided on substantially U-shaped member 235 permits movement of the L-shaped member 235 relative to the armature member 303 in order to provide a secondary adjustment between the armature member 303 and the eccentric cam surface 225 of the adjusting rod 207.

FIGURE 3 shows the two extreme magnetic air gap positions A and B (wherein the position A of the armature member 303 is shown in dotted fashion). The air gap position B shows the maximum air gap adjustment provided by the adjustment assembly 290 while the position A shows the minimum air gap position provided by the assembly 22th). It should be understood that any plurality of positions between the extreme positions A and B is obtainable with the adjustment assembly 200 of the instant invention. The discreet positions, which may be arbitrarily selected depending upon the individual circuit breaker application may be further facilitated in the manner shown in FIGURE 5. In this example, the entire mag netic trip assembly 3d0 and adjustment assembly 200 may be completely enclosed by a housing 400, only a portion of which has been shown for purposes of clarity. The housing 400 is provided with a suitable aperture 401 for receipt of the upper end of adjusting rod 207. A groove 250 is provided on the upper surface of rod 207 for receiving an adjusting tool, such as for example, a screw driver. The upper surface of the housing 456 is then provided with suitable letter and numeral designations 402-407 which cooperate with an arrow, or pointer, 251, provided on the top surface of adjusting button 207. In this manner, simply by lining up the pointer 251 with the discreet position lines EM-407, a plurality of air gap adjustments are readily obtainable.

It should be noted that the substantially linearly mo- 7 tion experienced by the armature member 303 and substantially L-shaped member 235 is imparted directly thereto by means of the adjusting rod 207 without providing any connecting linkages or translational members therebetween. Thus, any rotary motion of the adjusting rod 207 is directly imparted (in the form of linear motion) to the armature member 3%. In addition thereto, the adjusting rod 207 undergoes substantially no linear motion, either up or down, in the vertical direction, thereby substantially simplifying the adjusting operation for the operator, making it a simple rotational motion and further, enabling the adjustment to be made by moving the adjusting rod 2%? in either clockwise or counterclock vise direction since no locking means is provided Which prevents a full 360 degree cycle of rotation. In order to eliminate the guess Work of accurately positioning the adjusting rod 297, the ear 217a of spring means 214, together With the radially aligned grooves 222 in upper surface 221 of flange 22d facilitate and completely control the adjustment of the air gap means.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those sk'lled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. Manually operable armature positioning means for adjusting the air gap of a circuit breaker magnetic trip assembly comprising bracket means for mounting said adjusting means to a circuit breaker; an adjusting rod, said racket means receiving therein said adjusting rod to enable rotation of said rod about its central axis; first means secured to said rod for abutting said bracket means; second means secured to said bracket means for abutting said adjusting rod; said first and second means preventing said adjusting rod from any linear movement along its central axis; one end of said adjusting rod having a cam surface; a first member having an extending arm; said member positioned for securement to the magnetic trip armature; said extending arm positioned to slidably engage said cam surface; said adjusting rod constructed to move said first member substantially in a linear direction due to the rotation of said adjusting rod for positioning the magnetic trip assembly armature.

2. Manually operable armature positioning means for adjusting the air gap of a circuit breaker magnetic trip assembly comprising bracket means for mounting said adjusting means to a circuit breaker; an adjusting rod, said bracket means receiving therein said adjusting rod to enable rotation of said rod about its central axis; first means secured to said rod for abutting said bracket means; second means secured to said bracket means for abutting said adjusting rod; said first and second means preventing said adjusting rod from any linear movement along its central axis; one end of said adjusting rod having a cam surface; a first member having an extending arm; said member positioned for securement to the magnetic trip armature; said extending arm positioned to slidaibly engage said cam surface; said adjusting rod constructed to move said first member substantially in a linear direction due to the rotation of said adjusting rod for positioning the magnetic trip assembly armature; said adjusting rod having a second surf-ace slidably engaged by said bias means; said surface having at least one groove cooperating with said bias means for maintaining said adjusting rod in a predetermined angular position.

3. Manually operable armature positioning means for adjusting the air gap of a circuit breaker magnetic trip assembly comprising bracket means for mounting said adjusting means to a circuit breaker; an adjusting rod, said bracket means receiving therein said adjusting rod to enable rotation of said rod about its central axis; first means secured to said rod for abutting said bracket means; second means secured to said bracket means for abutting said adjusting rod; said first and second means preventing said adjusting rod from any linear movement 8 along its central axis; one end of said adjusting rod having a cam surface; a first member having an extending tarm; said member positioned for securement to the magnetic trip armature; said extending arm positioned to slidably engage said cam surface; said adjusting rod constructed to move said first member substantially in a linear direction due to the rotation of said adjusting rod for positioning the magnetic trip assembly armature; said adjusting rod having a second surface slida'bly engaged by said bias means; said surface having at least one able rotation of said rod about its central axis; first means secured to said rod for abutting said bracket means; second means secured to said bracket means for abutting said adjusting rod; said first and second means preventing said adjusting rod from any linear movement along its central axis; one end of said adjusting rod having a cam surface; a first member having an extending arm; said member positioned for securement to the magnetic trip armature; said extending arm positioned to slidably engage said cam surface; said adjusting rod constructed to move said first member substantially in a linear direction due to the rotation of said adjusting rod for positioning the magnetic trip assembly armature; said adjusting rod having a second surface substantially perpendicular to said cam surface slidably engaging said bias means; said second surface having a plurality of radially aligned grooves; each of said grooves being adapted to cooperate With said .bias means to retain said adjusting rod in a plurality of predetermined angular positions.

5. Manually operable armature positioning means for adjusting the air gap of a circuit breaker magnetic trip assembly comprising bracket means for mounting said adjusting means to a circuit breaker; an adjusting rod, said bracket means receiving therein said adjusting rod to enable rotation of said rod about its central axis; first means secured to said rod for abutting said bracket means, second means secured to said bracket means for abutting said adjusting rod; said first and second means preventing said adjusting rod from any linear movement along its central axis; one end of said adjusting rod having a cam surface; a first member having an extending arm; said member positioned for securement to the magnetic trip armature; said extending arm positioned to slidably engage said cam surface; said adjusting rod constructed to move said first member substantially in a linear direction due to the rotation of said adjusting rod for positioning the magnetic trip assembly armature; said adjusting rod having a second surface substantially perpendicular to said cam surface slidably engaging said bias means; said second surface having a plurality oi radially aligned groove-s; each of said grooves being adapted to cooperate with said bias means to retain said adjusting rod in a plurality of predetermined angular positions; said bias means having at least one resilient arm; the free end of said arm being formed to be received by each of said grooves for maintaining said adusting rod in any of said predetermined angular positions.

References Cited by the Examiner FOREIGN PATENTS 897,309 5/62 Great Britain.

JOHN F. BURNS, Primary Examiner. 

1. MANUALLY OPERABLE ARMATURE POSITIONING MEANS FOR ADJUSTING THE AIR GAP OF A CIRCUIT BREAKER MAGNETIC TRIP ASSEMBLY COMPRISING BRACKET MEANS FOR MOUNTING SAID ADJUSTING MEANS TO A CIRCUIT BREAKER; AN ADJUSTING ROD, SAID BRACKET MEANS RECEIVING THEREIN SAID ADJUSTING ROD TO ENABLE ROTATION OF SAID ROD ABOUT ITS CENTRAL AXIS; FIRST MEANS SECURED TO SAID ROD FOR ABUTTING SAID BRACKET MEANS; SECOND MEANS SECURED TO SAID BRACKET MEANS FOR ABUTTING SAID ADJUSTING ROD; SAID FIRST AND SECOND MEANS PREVENTING SAID ADJUSTING ROD FROM ANY LINEAR MOVEMENT ALONG ITS CENTRAL AXIS; ONE END OF SAID ADJUSTING ROD HAVING A CAM SURFACE; A FIRST MEMBER HAVING AN EXTENDING ARM; SAID MEM- 